You can down load uPlay from a few spots. The easiest is most likely going to eShop. Once you got the App, it will synch to the Ubisoft games you own (for me ZombiU/AC:3). You get points for doing certain things that unlock additional content in the Ubisoft game.
I believe you have to go to uPlay, pick the game, and then use the points to unlock additional content, but I may be a little off (this is what I remember doing). --- NNID: Minny612 3DS FC: 5155-2933-9036